Easy avg velocity problem I can't figure out

In summary, the average velocity is 25 miles per hour for the first half of the trip and 40 miles per hour for the second half of the trip.
  • #1
weeeee123
3
0

Homework Statement


First half of a trip is @ 10 MPH
Second half of a trip is @ 40 MPH
Avg velocity?

Homework Equations


(Vi+Vf)/2 = avg velocity...?

The Attempt at a Solution


K, this is obviously a simple question but for some reason when I do it I get it wrong, and I'm 100% sure I'm right. But I'm not. WTH?

I know the answer is 16, because the answer is given to me. I don't know how to get to there though for whatever reason. What I did was basically weight each velocity by multiplying each by .5 since each speed is for half the time. I get 25, which is wrong. Then I thought about it this way. If I go 10 MPH for half an hour, that's 5 miles. Then if I go 40 MPH for half an hour, that's 20 miles. In total I went 25 miles in one hour, and my avg velocity should be 25 in that case. What am I missing?
 
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  • #2
weeeee123 said:

Homework Statement


First half of a trip is @ 10 MPH
Second half of a trip is @ 40 MPH
Avg velocity?

Homework Equations


(Vi+Vf)/2 = avg velocity...?


The Attempt at a Solution


K, this is obviously a simple question but for some reason when I do it I get it wrong, and I'm 100% sure I'm right. But I'm not. WTH?

I know the answer is 16, because the answer is given to me. I don't know how to get to there though for whatever reason. What I did was basically weight each velocity by multiplying each by .5 since each speed is for half the time. I get 25, which is wrong. Then I thought about it this way. If I go 10 MPH for half an hour, that's 5 miles. Then if I go 40 MPH for half an hour, that's 20 miles. In total I went 25 miles in one hour, and my avg velocity should be 25 in that case. What am I missing?

The equation that you wrote for the average velocity is incorrect. Instead, the average velocity is the total distance divided by the total time. Try it that way instead.

(Don't worry -- this is a common error, and it's why they are asking you this question.)
 
  • #3
I quite honestly didn't even use that equation. I basically did what you said, dividing the total distance traveled by the total time.

avg vel = (40 *.5t + 10 *.5t)/t
= t(40*.5 + 10 * .5)/t
= (40 * .5 + 10 * .5)
= 25

ummm...?
 
  • #4
weeeee123 said:
I quite honestly didn't even use that equation. I basically did what you said, dividing the total distance traveled by the total time.

avg vel = (40 *.5t + 10 *.5t)/t
= t(40*.5 + 10 * .5)/t
= (40 * .5 + 10 * .5)
= 25

ummm...?

When they say "first half" and "second half" of the trip, they mean in distance, not in time...
 
  • #5
berkeman said:
When they say "first half" and "second half" of the trip, they mean in distance, not in time...

Oh wow hahahahaha thank you
 

Related to Easy avg velocity problem I can't figure out

What is average velocity and why is it important?

Average velocity is the measure of the displacement of an object over a certain period of time. It is important because it helps us understand the rate at which an object is moving and how far it has traveled in a given time frame.

How do I calculate average velocity?

Average velocity is calculated by dividing the total displacement of an object by the total time it took to cover that displacement. The formula is: average velocity = total displacement / total time.

What are the units of average velocity?

The units of average velocity are distance divided by time, such as meters per second (m/s) or kilometers per hour (km/h).

What if there are different velocities at different points in time?

If there are different velocities at different points in time, you can calculate the average velocity by finding the total displacement over the total time, just as in the formula. However, this will only give you the average velocity for the entire period of time and not at specific points in time.

How can I use average velocity in real life?

Average velocity can be used in various real-life scenarios, such as calculating the speed of a car, the rate of a runner, or the velocity of a projectile. It can also be used in more complex situations, such as calculating the average speed of a roller coaster or the average velocity of a rocket during launch.

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